Many countries set strict standards for noise exposure of personnel operating in environments where they may experience excessive noise levels and accumulated exposure time, such as a workplace. These standards specify values for noise level parameters including the accumulated (integrated) amount of noise, the maximum level of noise and peak level (eg. 140 dB) to which an individual has been exposed during a workshift. Standards may also regulate other noise parameters.
In many jurisdictions, individuals exposed to noiseover a predetermined value (in the US the value is 85 dBA Time Weighted Average (TWA)) are required to be included in a hearing conservation program, where they are individually monitored for noise exposure and regular hearing tests are required.
In order to comply with the standards and to ensure that personnel are protected, it is necessary for organisations to monitor noise levels in the environment where the personnel are operating and to assess individuals' exposure to noise (as well as providing regular hearing tests).
Conventionally, audio or noise dosimeters are used to monitor noise levels. These devices include a detector, such as a microphone, for detecting noise, and electronic circuitry for determining noise level in the detection area. Dosimeters are used in two ways:    1. To sample noise within areas in the environment by being placed within the areas for a predetermined period of time;    2. To sample noise levels experienced by a person by occasional wearing of dosimeters by individuals. Noise dosimeters are, therefore, “sampling” devices.
They provide samples of ambient noise from which subsequent calculations are made to estimate noise exposure for personnel.
They are complex to operate and must be implemented by professionally trained staff, such as acousticians and industrial safety hygienists. They provide technical data which require professional interpretation.
Noise dosimeters, therefore, provide only occasional data from sampled areas in the workplace and require technical training to use.
The use of conventional noise dosimetry can, therefore, at best only provide an estimate of each individuals level of noise exposure. The estimate will be inaccurate for a number of reasons, including:    1. Workers tend to move from place to place within a workplace and not remain at their designated station, where noise level samples may have been taken.    2. Noise levels vary over time. Occasional sampling of noise levels (as with conventional dosimetry) does not, therefore, give a complete picture.    3. Each individual is not constantly monitored. The estimate of noise dosage that each individual is receiving cannot, therefore, be entirely accurate.    4. Conventional noise dosimetry provides no indication of an individual's compliance to wearing hearing protection equipment. Noise level and dosage estimates usually do not take into account hearing protection equipment that is required to be worn by an individual (for example, ear muffs and/or ear plugs) and furthermore if the individual does not comply, this will also affect the accuracy of the estimate.
Another problem with conventional monitoring techniques is that they do not provide the individual with any immediate feedback. On a day to day basis, therefore, an individual will not know whether the noise levels they have been exposed to may have exceeded the standard limits. They have no way of knowing.